Epidemiology of HIV/AIDS in adults in Malawi

Malawi monitors its HIV prevalence (number of HIV infections existing at a certain point in time) through sentinel surveillance at antenatal clinics (ANC). The most recent ANC sentinel data were collected from February to April 2003 and resulted in the HIV prevalence rates reported in table 2. Women who visit the antenatal clinic do not represent the general population and thus ANC prevalence data do not represent the prevalence in the general population. When compared with community-based samples ANC data generally overestimate the prevalence in young women (because ANC women are a selection of sexually active women) and underestimate the risk in older women (because ANC women are a selection of women less afflicted by factors like widowhood divorce and STI associated with fertility and HIV). Overall in sub-Saharan Africa ANC data overestimate the risk in men and underestimate the risk in women. Crampin and colleagues confirmed that this was indeed the case in Karonga district. Directly standardised estimates of men and women from ANC data were 9.4% and 9.2 % versus 11.4% and 13.9% in the community. The prevalence of HIV among sexually active women in Karonga who did not attend ANC was 27% against 12% in ANC women. (excerpt)